Parallel Lines

Lines AB and CD are parallel. Line EF is a transversal that cuts lines AB and CD.

Use points A, E, and F to change the values of the angles. We see that when there is a transversal cutting two parallel lines, relationships among angles form. 1. What do you notice about the angles formed by the transversal EF? 2. Do you think there will be angle pairs for non-parallel lines? Why?